Push-in tube connectors are well-known in the art wherein a preassembled fitting is employed into which the tube end is inserted with no further operation required for making the joint tight and leakproof. Such type connector finds particular use in assembly line operations, for example where tubing is being installed on truck air brake systems and the like.
Prior art devices of this type are exemplified for example in U.S. Pat. No. 4,188,051 wherein the general combination of components comprising a body and nut member, an elastomeric sealing ring and a collet type gripping element are employed to provide a fluid-tight seal upon insertion of tubing and a firm grip thereon to prevent withdrawal of same. Disconnection of such type coupling is made by unthreading the nut from the body member whereby the tubing and the internal components of the coupling can be withdrawn.
Another example of fitting employing similar components is shown in U.S. Pat. No. 4,062,572, this however being not of the strict push-in type, but rather requiring a final tightening of an exterior nut once the tubing is in position within the fitting to trap the gripper ring and establish a preferred compression of the elastomeric sealing member. Disconnection of this type fitting is also achieved by unthreading the nut.
This prior art exemplifies difficulties in fittings of these types. In the push-in variety sufficient axial play must be afforded to the internal components of the fitting since relative movement must occur between the conical surfaces of the gripper member and its conical seating surface to allow for radial expansion and contraction thereof. With the components loosely assembled in the fitting in such manner, there occurs the possibility of cocking of the gripper sleeve, for example, unless means are provided to maintain alignment. Further, such axial end play may affect the sealing characteristics of the elastomeric seal as pulsations are encountered in fluidpower systems causing movement of the components in the fitting and further the possibility of weakening of the wall of the tubing can occur due to the play allowed. It is noted in various of these prior art embodiments that backup or secondary seals are provided between body and nut members to assure fluid tight connections.
While perhaps a more reliable seal can be effected in the type of fitting disclosed in U.S. Pat. No. 4,062,572 in that a controlled compression can be made to occur in the elastomeric seal and end play reduced or eliminated, such fitting is difficult to use in requiring the manual tightening of the nut portion thereon after the tubing has been inserted in the fitting.